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From: Eric Dumazet <eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Simon Horman <horms-/R6kz+dDXgpPR4JQBCEnsQ@public.gmane.org>
Cc: dev-yBygre7rU0TnMu66kgdUjQ@public.gmane.org,
	netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
Subject: Re: [PATCH net-next] udp: intoduce udp_encap_needed static_key
Date: Thu, 12 Apr 2012 11:10:11 +0200	[thread overview]
Message-ID: <1334221811.5300.6021.camel@edumazet-glaptop> (raw)
In-Reply-To: <1334221528.5300.6008.camel@edumazet-glaptop>

On Thu, 2012-04-12 at 11:05 +0200, Eric Dumazet wrote:

> If static_key is not yet enabled, the fast path does a single JMP .
> 
> When static_key is enabled, JMP destination is patched to reach the real
> encap_type/encap_rcv logic, possibly adding cache misses.

Small note Simon,

The jump trick is effective on x86 (and maybe some other arches) when

CONFIG_JUMP_LABEL=y

Else, its replaced by atomic_read(...) > 0, a cnditional jump but
reading a read_mostly/shared variable, instead of a per socket field.

  reply	other threads:[~2012-04-12  9:10 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-12  7:42 [RFC v3] Add TCP encap_rcv hook Simon Horman
     [not found] ` <20120412074159.GA10866-/R6kz+dDXgpPR4JQBCEnsQ@public.gmane.org>
2012-04-12  8:20   ` Eric Dumazet
2012-04-12  9:05     ` [PATCH net-next] udp: intoduce udp_encap_needed static_key Eric Dumazet
2012-04-12  9:10       ` Eric Dumazet [this message]
2012-04-12 14:35       ` Simon Horman
     [not found]         ` <20120412143552.GA8730-/R6kz+dDXgpPR4JQBCEnsQ@public.gmane.org>
2012-04-12 14:40           ` [RFC v4] Add TCP encap_rcv hook Simon Horman
2012-04-13 17:41       ` [PATCH net-next] udp: intoduce udp_encap_needed static_key David Miller
     [not found]         ` <20120413.134108.1844473866612154303.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
2012-04-13 17:45           ` Benjamin LaHaise
2012-04-12 13:10     ` [RFC v3] Add TCP encap_rcv hook Simon Horman

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